Science Advisory Report  2012/062

Stock Assessment Report on Pacific Herring in British Columbia in 2012

Summary

  • The five major BC herring stocks are Haida Gwaii (Area 2E), Prince Rupert District, Central Coast, Strait of Georgia, and West Coast of Vancouver Island, while the two minor herring stocks are Area 2W and Area 27 (Figure 1).
  • The Fishery Management Framework establishes harvest control rules setting the maximum available commercial harvest for each of the major stock areas at 20% of the forecast of mature stock biomass (males and females combined) when the forecast of mature stock biomass is above the commercial fishery threshold or “cutoff”, which is 25% of estimated unfished biomass (0.25 B0). If a forecast exceeds a cutoff, but a 20% harvest rate would result in spawning biomass that is less than the cutoff, the maximum available harvest is determined as the difference between the forecast and cutoff.
  • An integrated statistical catch age model (ISCAM) was used to assess the 2012 herring spawning stock biomass, and forecast the 2013 pre-fishery mature stock biomass. The ISCAM model was first reviewed and implemented for the 2011 assessment cycle. Further sensitivity analyses were conducted and reviewed in June of 2012, leading to a recommendation for continued use of the ISCAM model for the 2012 assessment cycle. Additional recommendations include the development of limit and upper stock reference points, compliant with the precautionary approach.
  • The following is a summary of the assessment results and advice by management area. All herring biomass results are based solely on output from the 2012 assessment model. Biomass is reported in metric tonnes and all estimates represent median values (and 90% confidence intervals in parentheses) from the joint posterior distribution. Bt denotes estimates of spawning stock biomass.

Haida Gwaii (HG, Area 2E)

  • All herring spawning from Cumshewa Inlet in the north to Louscoone Inlet in the south are assumed to be part of the Haida Gwaii stock.
  • No commercial herring fishery occurred in this area in 2012 (or 2003-2011).
  • The median estimate of the 2012 spawning stock biomass is 17,547 (9,349 – 32,723) tonnes.
  • The forecast of mature stock biomass for 2013 is 8,935 (4,843 – 17,225) tonnes (assuming poor recruitment), which is slightly above the fishing threshold of 0.25B0 (8,892 tonnes).
  • Spawner biomass has remained at a stable but low level over the past 10 years, and there is uncertainty about the cause of current low productivity. Given that there has been limited stock recovery, even in the absence of commercial fisheries, an assessment to determine appropriate rebuilding and harvest strategies is recommended prior to reopening fisheries in this area.

Prince Rupert District (PRD)

  • All herring spawning in Statistical Areas 3 to 5 are assumed to belong to the Prince Rupert District stock.
  • In 2012, the total roe herring seine fishery validated catch was 466 tonnes and the total roe herring gillnet fishery validated catch was 917 tonnes.
  • A commercial spawn-on-kelp fishery occurred in this area in 2012.
  • The median estimate of the 2012 post fishery spawning biomass is 26,857 (15,350 – 46,398) tonnes.
  • The forecast of mature stock biomass for 2013 is 26,168 (15,477 – 44,636) tonnes (assuming average recruitment), which is above the fishing threshold of 0.25B0 (19,107 tonnes).

Central Coast (CC)

  • All herring spawning in Kitasu Bay (a portion of Statistical Area 6), in Statistical Area 7, and in part of Statistical Area 8 (Kwakshua Channel and Fitzhugh Sound) are assumed to be part of the Central Coast stock.
  • No commercial herring fishery occurred in this area in 2012 (or 2008-2011).
  • The median estimate of the 2012 post fishery spawning biomass is 13,747 (7,684 – 23,487) tonnes.
  • The forecast of mature stock biomass for 2013 is 10,032 (6,053 – 16,615) tonnes (assuming poor recruitment), which is below the fishing threshold of 0.25B0 (14,930 tonnes).
  • Spawner biomass has shown a steady decline over the past 13 years, remaining at low levels in the recent 5 years. There is uncertainty regarding the reason for the current low productivity. Given that there has been no evidence of stock recovery in the past 10-years, even in the absence of commercial fisheries, an assessment to determine appropriate rebuilding and harvest strategies is recommended prior to reopening fisheries in this area.

Strait of Georgia (SOG)

  • All herring spawning in Statistical Areas 14 to 19, 28 and 29 (excluding Section 293), and part of 13 (Herring Sections 132 and 135, Deepwater Bay area south) are assumed to belong to the Strait of Georgia herring stock.
  • In 2012, the total winter seine fishery (food and bait and special use) validated catch was 4,090 tonnes; the total roe herring seine fishery validated catch was 3,170 tonnes and the total roe herring gillnet fishery validated catch was 4,079 tonnes.
  • The median estimate of the 2012 post fishery spawning biomass is 97,802 (56,173 – 167,387) tonnes.
  • Spawner biomass has fluctuated over the past 10 years.
  • The forecast of mature stock biomass for 2013 is 82,952 (47,069 – 142,361) tonnes (average recruitment forecasted based on summer trawl observations), which is above the fishing threshold of 0.25B0 (33,318 tonnes).

West Coast Vancouver Island (WCVI)

  • All herring spawning in Statistical Areas 23 to 25 are assumed to belong to the west coast of Vancouver Island herring stock.
  • No commercial fishery occurred on the west coast of Vancouver Island in 2012 (or 2006-2011).
  • The median estimate of the 2012 post fishery spawning biomass is 13,698 (7,490 – 24,095) tonnes.
  • The forecast of mature stock biomass for 2013 is 10,989 (6,971 – 17,978) tonnes (poor recruitment forecasted based on summer trawl observations), which is below the fishing threshold of 0.25B0 (14,067 tonnes).
  • Science voiced concerns over data quality for 2012 (such as missing spawn and low number of biological samples).
  • Spawner biomass has remained at relatively low levels and there is uncertainty about the cause of current low productivity. Given that there has been limited stock recovery, even in the absence of commercial fisheries, an assessment to determine appropriate rebuilding and harvest strategies is recommended prior to reopening fisheries in this area.

Area 2W

  • All herring spawning in Statistical Area 2W (except Herring Section 006) are assumed to belong to this Haida Gwaii minor stock.
  • A commercial spawn-on-kelp fishery occurred in this area in 2012.
  • The median estimate of the 2012 post fishery spawning biomass is 5,707 (2,421 – 12,103) tonnes.
  • The forecast of mature stock biomass for 2013 is 5,327 (1,923 – 12,630) tonnes (assuming average recruitment).

Area 27

  • All herring spawning in Statistical Area 27 are assumed to belong to this West Coast of Vancouver Island minor stock.
  • A commercial spawn-on-kelp fishery occurred in this area in 2012.
  • The median estimate of the 2012 post fishery spawning biomass is 1,109 (588 – 2,101) tonnes.
  • The forecast of mature stock biomass for 2013 is 1,154 (663 – 2,077) tonnes (assuming average recruitment).

This Science Advisory Report has resulted from the Fisheries and Oceans Canada, Canadian Science Advisory Secretariat Pacific Regional Advisory Meeting of September 5-6, 2012 on Pacific Herring Stock Assessment. Additional publications from this process will be posted as they become available on the DFO Science Advisory Schedule.

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